Segregation analysis of the family data collected in this project provides evidence for an autosomal dominant genetic susceptibility to epilepsy in approximately 9% of families. In the next phase of the project, we propose to validate this genetic model, describe in detail the clinical manifestations of seizure disorders in families likely to have a genetic susceptibility, assess the power of the data for a future genetic linkage analysis, and collect blood samples to be used in a future linkage study if the genetic model proves valid. The results of segregation analysis will be used to select 40 families very likely to be segregating the putative susceptibility allele. These families will be extended by collecting information on all first-degree relatives of individuals with epilepsy. The validity of the segregation analysis model will then be tested by using the parameters of the model to predict occurrence of epilepsy in newly ascertained family segments, and testing consistency with observation. Clinical manifestations of seizure disorders in the families likely to have a genetic susceptibility will be described in detail, using standardized clinical assessments involving direct interviews, neurological examinations, and electroencephalograms (EEGs). These new data will also be used to assess the validity of previous diagnoses (based on telephone interviews) through comparison with the new diagnoses (based on personal examinations and EEGs). In anticipation of a future genetic linkage study, expected lod scores will be calculated in the families with a putative genetic susceptibility using the computer program SIMLINK, and blood samples from first-degree relatives and spouses of individuals with epilepsy will be collected and stored for possible future use.